Lean Body Mass Formulas Explained
Three main formulas estimate LBM from weight and height:
Boer (1984) — Most Accurate: Men: 0.407 × W(kg) + 0.267 × H(cm) − 19.2. Women: 0.252 × W(kg) + 0.473 × H(cm) − 48.3.
James (1976): Men: 1.1 × W − 128 × (W/H)². Women: 1.07 × W − 148 × (W/H)².
Hume (1966): Men: 0.3281 × W + 0.3393 × H − 29.5. Women: 0.29569 × W + 0.41813 × H − 43.3.
What Is FFMI?
Fat-Free Mass Index (FFMI) = LBM(kg) / height(m)². Average natural FFMI for men is 18–20; women 14–17. Values above 25 for men are associated with performance-enhancing drug use in studies. Source: Kouri et al., New England Journal of Medicine, 1995.
Boer LBM = (0.407 × 80) + (0.267 × 180) − 19.2 = 32.56 + 48.06 − 19.2 = 61.4 kg LBM
Fat mass = 80 − 61.4 = 18.6 kg | Body fat % = 23.3%
FFMI = 61.4 / (1.80)² = 18.9 (average natural range)
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Formula sourced from: Reserve Bank of India • EPFO • Income Tax Dept India • SEBI • IRS (USA)
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